1. Field of the Invention
The present invention relates to a vehicle headlight apparatus, which performs a headlight operation, in which a direction of an optical axis of a headlight is changed in accordance with a traveling condition of a vehicle.
2. Description of Related Art
Conventionally, there has been proposed an adaptive front-lighting system (AFS) that radiates light in a direction, which a driver of a vehicle desires. The AFS is realized by changing a lighting direction (i.e., a direction of an optical axis) of a headlamp (headlight) of the vehicle. The AFS includes a leveling mechanism and a swivel mechanism for changing a direction of the optical axis of the headlamp. Here, the leveling mechanism vertically changes the direction of the optical axis, and the swivel mechanism horizontally changes the direction of the optical axis.
In the swivel mechanism of the above mechanisms, an actuator for changing the direction of the optical axis of the headlamp is driven based on input data, such as a headlamp switch signal, a vehicle speed and a steering angle. The swivel mechanism is permitted to be operated only when the vehicle travels in a forward direction. In contrast, when the vehicle travels in a backward direction, the above swivel mechanism is not permitted to be operated by a law because of security. Specifically, in a conventional vehicle having an automatic transmission (A/T vehicle), it is determined whether the vehicle travels in the forward direction based on an input signal of a shift position. Typically, the vehicle needs to travel in the forward direction in order to allow the swivel operation to be executed. When the inputted shift position signal indicates other than R (reverse drive position) or N (neutral position), that is, for example, P (parking position), L (first gear position), 2 (second gear position), D (forward drive position), it is determined that the vehicle travels in the forward direction (see Japanese Unexamined Patent Publication No. H8-142743).
However, in the above conventional technology for detecting whether the vehicle travels in the forward direction, it is a disadvantageous that the conventional technology cannot detect the actual traveling direction of the vehicle because the shift position only indicates the position of the shift lever. For example, when the shift position indicates N, it is impossible to detect the actual state of the vehicle (e.g., traveling in the forward direction, traveling in the backward direction or stopping) depending only on the information.
In a vehicle having a manually shifted transmission (M/T vehicle), a change lever corresponds to the shift lever in the A/T vehicle. In contrast to the A/T vehicle, the M/T vehicle is not designed in such a manner that signals are outputted based on a detected position of the change lever. Therefore, the traveling state of the vehicle cannot be detected based on the outputted signals. It is not certain that the installation of an additional device, which detects the position of the change lever to output a signal, is impossible from a technical point of view. However, it is disadvantageous that a cost will be increased when the additional device is provided. Also, it is disadvantageous that the actual traveling state of the vehicle cannot be detected similarly to the A/T vehicle when the change lever is located at the N position even in a case of the installation of the additional device.